Device for process monitoring in a deposition welding method

ABSTRACT

The invention relates to a device and a method for process monitoring in a deposition welding method. The object of the invention is to provide a device in which the process monitoring in a deposition welding method is further optimized, and process deviations that can affect the quality of a product are reliably avoided. Surprisingly, the devices known in the state of the art for process monitoring in deposition welding can be developed to a substantially optimized process monitoring, in which said devices are supplemented by equipment for detecting a time period during which the detected surface region is greater than a predetermined minimum value, and equipment for discontinuing the deposition welding process in an automated manner in the event that the time period of the detected surface region is greater than a predetermined time value.

DESCRIPTION

The invention relates to device for process monitoring in a depositionwelding method according to the preamble of claim 1 and a method forprocess monitoring in a deposition welding method according to thepreamble of claim 5.

In the field of additive manufacturing individual layers all the way to3D structures, among other things, laser-powder deposition welding isused among other things, which pertains to the deposition weldingmanufacturing method (or also referred to as cladding). Thereby, amelting of the workpiece surface takes place on a workpiece by means oflocalized heat exposure while simultaneously applying almost any type ofmetallic material. Thereby, nowadays, a high-performance diode laser orfiber laser is primarily used as a heat source.

In order to obtain the desired quality and surface characteristic, acontinuous process monitoring is required. Using a camera system, whichis optically directed onto the point where melting occurs, an image ofthe region to be monitored can be generated. Thereby, as a general rule,temperature values and temperature intensities are generated by thepoint where melting occurs, which can be used later on for monitoringand controlling the process.

A device to carry out the surface treatment of a workpiece surface byapplying heat is known from DE 10 2007 032 190 A1. Thereby, theeffective range of processing is converted into image signals and then,processed into control signals in order to control the heating effect onthe surface of the workpiece depending on the state of the effectiverange of the heat. The control signals cause the actuation of one or aplurality of actuators to change the heating effect. Thereby, for theprocessing of the image signals, a pixel-by-pixel analysis is used wherethe image appears based on the grey-shade gradients, which is dividedinto a heat zone with a higher heat and a heat zone with a lower heat.The evaluation of the progression and quality of the process therebytakes place only based on the pixel-by-pixel comparison of the regionsize of these two heat zones with each other.

From DE 10 2004 051 876 A1, an arrangement for the locally resolvedtemperature measurement for a laser processing method is known. Thereby,a specifiable processing region of a workpiece can be depicted on anoptical detector measuring in a locally resolved manner. Furthermore, anoptical filter is arranged in the beam path between the processingregion and the optical detector, which blocks the electromagneticradiation of one or a plurality of laser processing beam(s). Thecaptured image of the detector can be used for the determination of thetemperature distribution of the processing region, among other things.For the evaluation of the captured image, only the shape and theposition of a region are taken into account, which exceeds a specifiedmaximum temperature value.

US 2008/0296270 A1 discloses a real-time control system of a depositionwelding process where the temperature is monitored by means of apyrometer and the shape of the molten pool is monitored by means of acamera.

From U.S. Pat. No. 6,423,926 B1, a method is known where the temperatureof a nozzle is monitored during a laser deposition welding method bymeans of thermal elements that are arranged within a process head.

U.S. Pat. No. 6,940,037 B1 discloses a control system for a depositionwelding process where the welding parameters are adjusted based oncladding points and the determination of a geometric factor.

EP 1 600 247 A2 shows a device for monitoring a nozzle of a laser-beammachine, wherein the device is arranged separately from a process headfor monitoring and uses a CCD camera for the optical monitoring of anozzle.

From US 2004/0133298 A1, a device is known where a laser depositionwelding method controls the cladding process by means of opticallydetecting the roughness, the cladding dimensions and the hardening speedof the deposited material.

The object of the invention is to provide a device in which the processmonitoring in a deposition welding method is further optimized, andprocess deviations that can affect the quality of a product are reliablyavoided.

The task is achieved by means of a device for process monitoring in adeposition welding method according to claim 1 and by means of a methodfor process monitoring in a deposition welding method according to claim5.

Favorable embodiments and further embodiments of the invention can beachieved by means of the features referred to in the subclaims.

The device according to the invention for process monitoring in adeposition welding method comprises an optical detector, which isoptically integrated within a beam path of a laser beam, wherein thelaser beam is emitted by a laser-beam source in a directed manner tomelt a material to be deposited, is guided onto a workpiece via anoptical system and, thereby, focused onto a surface of the workpiece tobe processed, and the optical system is set up to send a detector signaldepending on the temperature of the workpiece and the nozzle geometry inthe direction opposing the laser beam to an optical detector, which iscaptured by the optical detector and converted into an electricaldetector signal, comprises a conversion unit, which converts theelectrical detector signal into an image, which reproduces thetemperature-dependent intensity distribution of the detector signalcaptured by the optical detector, and comprises an evaluation unit,which is set up to further process the image, wherein the evaluationunit furthermore comprises the following for this purpose: equipment todetermine a monitoring region of the image, a device for the repeateddetection of a surface region of the monitoring region, in which theintensity exceeds a specified minimum value, a device to detect a timeperiod, during which the detected surface region greater than aspecified minimum value, and a device to discontinue the depositionwelding process if the time period of the detected surface region isgreater than a specified time value.

Surprisingly, the devices described in the above and known in the stateof the art for process monitoring in deposition welding can be developedto a substantially optimized process monitoring, in which said devicesare supplemented by equipment for detecting a time period during whichthe detected surface region is greater than a predetermined minimumvalue, and equipment for discontinuing the deposition welding process inan automated manner in the event that the time period of the detectedsurface region is greater than a predetermined time value.

This is based on the circumstance that the inventors have recognizedthat, in this way, a device can be created, which makes it possible todetect nozzle adhesive substance residues from the deposition weldingprocess in a reliable and timely manner during their occurrence.

Such adhesive substance residues can occur if, during the depositionwelding process, powder already begins to melt at the outlet opening ofa nozzle for the supply of powder, and spreads in the direction of thepassage opening of the laser beam over time and limit this or enclosedgas bubbles are freed within the workpiece and, by means of this,material melted on the workpiece spurts away and it adheres to the edgeof the passage opening of the laser beam. The problem with such adhesivesubstance residues is that, while projecting into the passage of thelaser beam, this results in limiting the laser beam (meaning less energyapplication onto the workpiece than is planned) or in the reflection ofthis within the nozzle, which, in turn, can result in excessive heatingof the nozzle. In addition, the adhesive substance residue can form atthe outlet opening of the powdery material of the nozzle and stronglyinfluence the focusing of the powdery material.

In order to detect a possible fault in the focusing of the powder coneas early as possible, a constant process monitoring is required. Itpermits for the timely detection of any change, no matter how small itis, with regard to the adhesive substance residue of molten material,which stabilizes the quality of the product significantly.

The invention thereby creates a device, by means of which such adhesivesubstance residues can be reliably detected and furthermore ensuresthat, in the case of detecting a continuous adhesive substance residueof dirt at the nozzle opening, the process is automatically ended.

The device according to the invention can be favorably further developedin such a way that the monitoring region is an annular edge region alongthe inner circumference of the nozzle opening (nozzle edge), which isparticularly favorable for the detection of adhesive substance residues,which can typically form on the nozzle edge.

By means of this, it can be ensured that nozzle adhesive substanceresidues, which can form on the edge of the nozzle, are reliablydetected by the device.

The device according to the invention can be favorably further developedin such a way that the equipment is set up to discontinue the depositionwelding process in order to discontinue the process of depositionwelding in an automated manner if the time period of the detectedsurface region is greater than a specified time value.

By means of an automated process, a quick response can be taken for anychanges in the monitoring region and, if required, the process can bestopped in a timely manner if the optical detection of the adhesivesubstance residues exceeds the previously determined limit values. Thisincreases the reliability of the process sequence.

The device according to the invention can additionally be favorablyfurther developed in such a way that the material to be deposited isguided via the nozzle, thereby focusing on the surface of the workpieceto be processed.

By means of this, the material, which should be deposited onto theworkpiece, can be guided into the focus of the laser beam in a selectivemanner, where it connects to the base material of the workpiece whichhas already been molten. Furthermore, such a focused supply is favorablesince increasingly smaller structures can be created by means of anincreased focusing of the powdery material.

The device according to the invention can be favorably further developedin such a way that the laser beam is guided through a middle region ofthe nozzle onto the surface of the workpiece to be processed.

The advantage of this further embodiment lies in that the laser beam iswithin the cone, which forms from the supply of the powdery material tobe deposited, thereby the material cone and the laser beam are able tolie close to one another. That has the advantage that the process head,which is moved over the workpiece and deposits the material on this, canbe relative compact, which is of a particular advantage for the creationof structures in regions that are difficult to reach.

The device according to the invention can be favorably designed in sucha way that the device is set up in such a way that a minimum size of themonitoring region is 20%, preferably at least 30%, being particularlypreferred at least 40%, however a maximum of 70% relative to an overallregion, consisting of the monitoring region.

Furthermore, the device is particularly favorably set up in such a waythat the specified minimum value for the detection of a time period is10%, preferably 15%, being particularly preferred 20% relative to therange of the monitoring region.

By means of this, different geometries of the nozzle can be taken intoconsideration and the device can be adapted to the deposition weldingconcerning the respective process parameters and requirements (such asquality of the weld, etc.).

The invention also comprises a method according to the invention forprocess monitoring in a deposition welding method under the use of anoptical overall system with an optical detector, which is integratedwithin a beam path of a laser beam, and with a laser-beam source, whichemits the laser beam from a laser-beam source in a directed manner tomelt material to be deposited, guides it on to a workpiece via anoptical system, thereby focusing it on to a surface of the workpiece tobe processed, and the optical system is set up to send a detector signaldepending on the temperature of the workpiece and the nozzle geometry inthe opposing direction of the laser beam to an optical detector, whichis captured by the optical detector and converted into an electricaldetector signal, and with a conversion unit, which converts theelectrical detector signal into an image, which reproduces thetemperature-dependent intensity distribution of the detector signalcaptured by the optical detector, wherein the method comprises thefollowing steps: Determination of the monitoring region of the image,repeated detection of a surface region of the monitoring region, inwhich the intensity exceeds a specified minimum value, detection of thetime zone, during which the detected surface region is greater than aspecified minimum value and discontinuing the process of the depositionwelding if the time period of the detected surface region is greaterthan a specified time value.

The invention divides the captured image of the intensities of theprocessing region into a plurality of regions in such a way that atleast one region is suitable for the monitoring of the nozzle adhesivesubstance residue and monitors the previously determined limit value forthe region size, intensity and time the region size exists. If theselimit value are exceeded in a certain sequence, the process isdiscontinued.

The method according to the invention can be favorably further developedin such a way that the monitoring region is determined as an annularedge region around the process region (nozzle edge) for the detection ofadhesive substance residues.

By means of this, it can be ensured that adhesive substance residues ofthe nozzle, which can form on the edge of the nozzle, can be reliablydetected by the method.

The method according to the invention can be favorably further developedin such a way that the time period is preferably one second, threeseconds or, being particularly preferred five seconds.

Thereby, the process monitoring can be given enough time to react to thechanges within the monitoring region. Thereby, it is of great importanceto select the time in such a way that the process is discontinued toquickly since, in the case of changes in the image of the monitoringregion, it can also only have to do with changes at short notice. Inturn, this would not be mandatorily indicate an adhesive substanceresidue on the nozzle edge and the process could be continued.

The method according to the invention can be favorably further developedin such a way that a minimum size of the monitoring region is at least20%, preferred at least 30%, being particularly preferred at least 40%,however, a maximum of 70% relative to the overall region consisting ofthe monitoring region and the process region.

By means of this, different shapes and diameters of the opening of thenozzle can be taken into consideration, just like other factors, whichare crucial for image processing (e.g. image scale, pixel number, etc.)

The method according to the invention can be favorably further developedin such a way that the specified minimum value for the detection of thetime period is a maximum of 10%, preferably a maximum of 15%, beingparticularly preferred a maximum of 20% relative to the minimum range ofthe monitoring region.

By means of this, the method can be applied to different nozzles/nozzlegeometries and furthermore, the method can be adapted to the depositionwelding concerning the respective process parameters and requirements(such as quality of the weld, etc.).

The invention is now explained in more detail based on the exemplaryembodiments. The figures show:

FIG. 1 : a diagram of a device according to the invention for processmonitoring in a deposition welding method,

FIG. 1 a : a detailed diagram of the evaluation unit of the deviceaccording to the invention for the process monitoring for a depositionwelding method according to FIG. 1 ,

FIG. 1 b : a beam path of the device according to the invention for theprocess monitoring for a deposition welding method according to FIG. 1 .

FIG. 2 : Cross section of a nozzle with a laser beam passing through andsupply of the material to be applied.

FIG. 3 : a diagram of a method according to the invention for processmonitoring in a deposition welding method,

FIG. 4 : detected image of a deposition welding process with adetermined monitoring region (left) according to the invention and thesame with an additionally recognizable adhesive substance residue to thenozzle (right).

FIG. 1 shows a schematic illustration of an exemplary embodiment of thedevice 100 for the process monitoring in a deposition welding methodwith an optical detector 10, which is optically integrated in a beampath of a laser beam 21. Favorably, this can take place via a beamsplitter as can be seen in FIG. 1 b , which is designed as a beamsplitter cube or a semipermeable mirror. By mean of this arrangement,the laser beam 21, which is guided from the laser-beam source 20 to theworkpiece 50, and, by means of this, material to be deposited 31 can bemelted, superimposed with a detector signal 11, which is set by thesurface 51 to be processed in an opposing direction to the laser beam 21to an optical detector 10. However, other embodiments are also possible,by means of which the laser beam and the detector signal can besuperimposed.

An optical sensor chip is used as a detector 10, which can detectinfrared wavelengths. They form the basis for the generation of an image61 with temperature-dependent intensities. For this purpose, inprinciple, cameras with a CCD or a CMOS sensor are used. They convertthe captured detector signal 11 into an electrical detector signal 12,which is sent to an evaluation unit 60.

In the conversion unit 70 itself, the electrical detector signal 12 canbe converted into the image 61 with the temperature-dependentintensities and sent to the integrated equipment 60 a, 60 b, 60 c, 60 dof the evaluation unit 60 for further processing.

Such an image 61 can be roughly divided into three regions, which can berecognized particularly well in FIG. 4 .

The first region is the process region. Here, particularly highintensities (high temperatures) can be expected in the image 61 since,here, the laser beam 21 hits the surface 51 of the workpiece 50 andthereby, a particularly higher heat application occurs. This region canbe recognized in FIG. 4 as the most inward region. This is not used forthe evaluation of the monitoring after adhesive substance residues ofthe nozzles.

The second region is the monitoring region, which is determined by theequipment 60 a, as will be explained later on in more detail, and usedfor the later evaluation with regard to the monitoring of the nozzleadhesive substance residues. This region extends on the outer edge ofthe process region in an annular way, as selected in this exemplaryembodiment in FIG. 4 . Expressed in other words, this means that theprocess region can be juxtaposed with the nozzle opening and therefore,the monitoring region extends along the edge of the nozzle opening.Here, as a rule, only average intensities (average temperature values)should be expected since, naturally, the heat, which is input by thelaser beam 21 into the workpiece 50, spreads within the material due toheat conduction, among other things.

The third region is the neutral region. This region comprises everythingexcept the first and the second region, as is shown in FIG. 4 . Here,except for a few artefacts, which arise, for example, from the reflectof the nozzle inner surface, comparably low intensities (lowtemperatures) are to be expected. Like the first monitoring region, thisregion is excluded from the monitoring with regard to adhesive substanceresidues of the nozzle.

FIG. 1 a shows a detailed diagram of the evaluation unit according tothe invention, the equipment of which should be explained in more detailbased on the following embodiments.

The equipment 60 a in FIG. 1 a determines the monitoring region 61 a,which is relevant to the further evaluation with regard to themonitoring after nozzle adhesive substance residues. Thereby, themonitoring region can assume a free shape or geometrically known shapes,such as that of a circular ring or a rectangular ring. Thereby, the sizeof the mould (such as, for example, the diameter, length extension,etc.) may vary. This depends on the respective parameters and thegeometry of the nozzle 30 used, which will still be explained later inmore detail. The size of the minimum range of the monitoring region 61 acan also be described relative to an overall region consisting of themonitoring region 61 a and the process region. Thereby, the values forthe minimum range of the monitoring region 61 a of at least 20% relativeto the minimum range of the overall region have emerged as beingexpedient.

The equipment 60 b in FIG. 1 a is used for the repeated detection of asurface region 61 b of the monitoring region 61 a. Thereby, the surfaceregion 61 b is detected where the intensity exceeds a specified minimumvalue 62. The detection itself takes place pixel by pixel due to thecharacteristics of the optical sensor chip 10 and comprises the size ofthe surface region 61 b, which is evaluated after detection.

The equipment 60 c in FIG. 1 a is used to detect a time period 61 c,during which the surface region 61 b detected by the device 60 b isgreater than a specified minimum value 63. That means that, in additionto detecting the intensity and the region size, in the case of exceedingthe intensity limit (specified minimum value) 62, the time the detectedsurface region 61 b exists occurs if, in addition to the intensity limit(specified minimum value) 62, a limit 63 of the region size has alsobeen exceeded. This is the third criterion for monitoring the image 61.The determination of the limit value 63 can also take place relative tothe minimum range of the monitoring region 61 a. Thereby, the values ofa maximum of 10% relative the minimum range of the monitoring region 61a have emerged as being expedient.

The equipment 60 d in FIG. 1 a serves to discontinue the depositionwelding process if the time period 61 c of the detected surface region61 b is greater than a specified time value 64. If the third criterionis also now exceeded in the case of monitoring the image 61, the dangeris great that, in the case of the detected region 61 b, it has to dowith a greater adhesive substance residue on the molten material on theedge of the nozzle 30. Due to this, the process is stopped.

Another favorable embodiment of the device 100 for the processmonitoring for a deposition welding method is shown in FIG. 2 . Here,the material to be applied 31 is guided via the nozzle 30 focusing onthe surface 51 of the workpiece 50 to be processed. By means of this,the focus of the material to be deposited 31 and the focus of the laserbeam 21 can be brought together, which results in a particularlyeffective processing of the supplied material 31. By means of this,finer structures can be generated during cladding.

In addition, the device 100 for process monitoring in a depositionwelding method can be favorably further developed, as is shown in FIG. 2, by means of the laser beam 21 being guided through a middle region ofthe nozzle 30 onto the surface 51 of the workpiece 50 to be processed. Avery compact construction of the process head is possible by means ofthis, which is of an advantage in the case of regions of the workpiece50 that are difficult to reach.

In FIG. 3 , a diagram of an exemplary embodiment of a method accordingto the invention for process monitoring in a deposition welding methodis shown. Thereby, in particular, the method steps of the evaluationunit 60 are shown.

At step S60 a, a monitoring region 61 a of the image 61 is determined.This monitoring region limits the image to the relevant range for theevaluation. Thereby, the values for the minimum range of the monitoringregion 61 a of at least 20% relative to the minimum range of the overallregion, consisting of a monitoring region 61 a and the process region,have emerged as being expedient.

At step S60 b, a surface region 61 b of the monitoring region 61 a isdetected again, in which the intensity exceeds a specified minimum value62. With the monitoring region relevant to the evaluation, regions aresearched for and these are detected, which exceed a previouslydetermined intensity limit and the detection of their region size pixelby pixel is started.

At step S60 c, a time period is detected, during which the detectedsurface region 61 b is greater than a predetermined limit value 63. Now,in the case of detecting the region size pixel by pixel, it is observedif a region, which can be coherent and cumulated, exceeds a previouslydefined pixel limit value 63. As an alternative, the determination ofthe limit value 63 can also take place relative to the minimum range ofthe monitoring region. If this is the case, the time of this regionexists is detected and the next step is started (S60 d).

Step S60 d discontinues the deposition welding process in the case, inwhich the time period of the detected surface region 61 b is greaterthan a specified time value 64. If the detected time of the region,which exceeds the intensity limit (specified minimum value) 62 and thelimit 63 of the size of the region, now also exceeds a time limit 64,the deposition welding process is discontinued since a greater adhesivesubstance residue of molten material to the edge of the nozzle 30 mustbe expected.

Thereby, for the selection of the time limit 64, a time period ofpreferably one second or of three seconds can be selected. Furthermore,in stochastic tests, a time period of five seconds has emerged as beingparticularly suitable since, in part, in the case of a process's timeperiod being too short, the process was discontinued although the nozzleadhesive substance residue was just about to change in such a way thatit would not have influenced the deposition welding process any more.

For determining the limit 63 of the size of the detected surface region61 b, depending on the geometry of the nozzle as well as the image scaleand other factors, which are crucial for image processing, at least 10%relative to the minimum range of the monitoring region 61 a has emergedas being expedient. Thereby, the different characteristics of the nozzlecould be dealt with and the requirements of, for example, quality of theweld could be taken into account.

1-4. (canceled)
 5. Method (S100) for process monitoring in a depositionwelding method under the use of an optical overall system with anoptical detector (10), which is optically integrated within a beam pathof a laser beam (21), and with a laser- beam source (20), which emitsthe laser beam (21) from a laser-beam source (20) in a directed mannerto melt material (31) to be deposited, guides it on to a workpiece (50)via an optical system (40), thereby focusing it on to a surface (51) ofthe workpiece (50) to be processed, and the optical system (40) is setup to send a detector signal (11) depending on the temperature of theworkpiece and a nozzle geometry of a nozzle (30) in an directionopposing the laser beam (21) to an optical detector (10), which iscaptured by the optical detector (10) and converted into an electricaldetector signal (12), and a conversion unit (70), which converts theelectrical detector signal (12) into an image (61), which reproduces thetemperature-dependent intensity distribution of the detector signal (11)captured by the optical detector (10), wherein the method comprises thefollowing steps: determining (S60 a) of a monitoring region (61 a) ofthe image (61), repeated (S60 b) detection of a surface region (61 b) ofthe monitoring region (61 a), in which the intensity exceeds a specifiedminimum value (62), detecting (S60 c) a time period (61 c), during whichthe detected surface region (61 b) is greater than a specified minimumvalue (63), and discontinuing (S60 d) of the deposition welding processif the time period (61 c) of the detected surface region (61 b) isgreater than a specified time value (64).
 6. Method (S100) for processmonitoring in a deposition welding method according to claim 5, whereina minimum size of the monitoring region (61 a) is determined in such away that it is at least 20% relative to an overall region predeterminedby the nozzle geometry consisting of the monitoring region (61 a) and aprocess region.
 7. Method (S100) for process monitoring in a depositionwelding method according to claim 6, wherein the specified minimum value(63) of the detected surface region (61 b) for the detection (S60 c) ofa time period (61 c) is 10% relative to the size of the monitoringregion (61 a).
 8. Method (S100) for process monitoring in a depositionwelding method according to claim 5, wherein the step of discontinuing(S60 d) the deposition welding process is performed in an automatedmanner.
 9. Method (S100) for process monitoring in a deposition weldingmethod according to claim 5, wherein the method further comprises thestep: guiding the material (31) to be deposited via the nozzle (30)focusing on the surface (51) of the workpiece (50) to be processed. 10.Method (S100) for process monitoring in a deposition welding methodaccording to claim 9, wherein the method further comprises the step:guiding the laser beam (21) through a middle region of the nozzle (30)to the surface (51) of the workpiece (50) to be processed.
 11. Method(S100) for process monitoring in a deposition welding method accordingto claim 5, wherein the monitoring region (61 a) is determined as anannular edge region around a process region.
 12. Method (S100) forprocess monitoring in a deposition welding method according to claim 1,wherein the specified time value (64) is 1 second or 3 seconds or 5seconds.
 13. A method, comprising the steps of: monitoring a region thatextends outwardly from a process region, where a laser beam hits aworkpiece surface to melt material on the workpiece surface, during adeposition welding process; and discontinuing the deposition weldingprocess in response to the monitored region having, for a time periodthat is greater than a predetermined time value, a temperature-dependentintensity distribution that exceeds a predetermined minimumtemperature-dependent intensity distribution value and a size that isgreater than a predetermined size limit value.
 14. The method accordingto claim 13, further comprising the steps of: sending a detector signalcorresponding to workpiece temperature and nozzle geometry; capturingthe detector signal, detecting infrared wavelengths of the captureddetector signal, and converting the captured detector signal into anelectrical detector signal; and converting the electrical detectorsignal into an image of the temperature-dependent intensitydistribution.
 15. The method according to claim 13, wherein themonitored region and the process region together define an overallregion; and the monitored region has a minimum size that is at 20% ofthe overall region.
 16. The method according to claim 15, wherein thepredetermined size limit value is 10% of the monitored region minimumsize.
 17. The method according to claim 13, wherein discontinuing thedeposition welding process comprises automatically discontinuing thedeposition welding process.
 18. The method according to claim 13,further comprising the step of: guiding the material deposited duringthe deposition welding process with a nozzle focused on the workpiecesurface.
 19. The method according to claim 18, further comprising thestep of: guiding the laser beam through a middle region of the nozzle tothe workpiece surface.
 20. The method according to claim 13, wherein themonitored region comprises an annular edge region around the processregion.